- Review from last week – GPS and LiDAR data
- Visualizing Point Cloud data (using Fusion)
- Build a DEM (DSM of DTM) using a script for White Box Tools
- Cleaning up the DEM (Raster data) – filling holes for “no data” values
- Raster Data Calculations
- Creating Watershed Raster Layers
- Create Web Ready 3D data (using qgis2threejs)
Review from Last Week
Visualizing Point Clouds in Fusion
We are using Fusion to look at point clouds that can be created using the LiDAR data from the city for the area around UNBC. You should have a desktop icon on your desktop for Fusion that launches the program. If you do not follow these steps:
- Download fusion from HERE
- Navigate to the folder you downloaded it to in the terminal (you can browse there in file explorer –> right click –> Open in terminal
- run this command wine fusionlatest.exe
- click to install any other programs necessary
- try the icon on your desktop again
- if that does not work use the following command to run it
- wine .wine/drive_c//FUSION/fusion.exe
Adding data to Fusion
Click the image button and load: /home/labs/enpl303/forest_for_the_world/allfour.bmp into the project.
Once that is done, load in the point cloud data by clicking the RAW Data button and adding the all4.las file
Viewing cloud data
- In the view draw a very small box around and area you may be interested in
- A circle will appear – it is now rendering the data
- We will go to the next step while we wait
Build the DEMS using scripts
There are several scripts in the folder we have been working in (Forest for the World), two of which will build a DTM and a DSM. Open up one of them in gedit to see what is inside the script (i.e. look at
terrain.sh). You will see it is the same commands we tried last week. We will make two new elevation models by:
- Copy the terrain.sh and surface.sh file to a folder for this week’s lab.
- right click on the files and set the permissions to all executing
- Open the terminal in that folder
- type –> ./terrain.sh
- type –> ./surface.sh
You will end up with two raster DEMs to open in QGIS
Cleaning up the DEMs created from the point clounds
Once the two DEMs are loaded into QGIS, you will notice holes in the data. Use the identity features button to see what the values are in the middle of Shane Lake. These holes suck as we cannot use the data for our work later on in the lab. We nee to clean it up. This is a simple operation in QGIS that is completed by:
- Going to the processing toolbox (if not activated –processing menu –> Toolbox)
- search for fill nodata
- launch the tool for both the surface and terrain DEMs keeping the defaults and creating new files (i.e terrain_filled.tif)
Height Calculations again
We are going to work with raster layers again next week (in combination with vector layers), so we will be seeing more of the raster calculator, but for now – create a difference raster file that shows vegetation heights in the scene. What do you notice in the scene? What is the rectangular looking feature int he middle of the raster images?
Create a Watershed layer from Terrain Model
Using the filled terrain model you have created (or using the ones in the Forest for the World folder). This is achieved by:
- open the r.watershed command in the processing toolbox
- Leave all the fields default except
- Ensure you have the filled DTM as the input layers
- Minimum size of exterior watershed –> 2
- Maximum length of surface flow –> 10000
- GRASS 7 region extent –> use the DTM as the extent
- Hit Run
There are some really interesting layers produced by this command. We will discuss them and their relevance to the work we will be doing in our next assignment. Load some data in from the /home/labs/geog300/unbc folder to compare against.
Create a new project
Lets start with new project in QGIS and shut down all other programs running. Throughout this lab, your workstation can take quite a pounding, so we should start fresh after awhile.
Load in the terrain and surface layers into Q again. Also load in the ortho imagery that the now larger extent covers. You can use the index file again (HINT: the one we used before ended in 444.tif – the other 3 are 441,442 and.443).
Add in another plugin
From the plugin menu add the qgis2threejs plugin. Now we are ready to make a web usable 3d scene. Follow these steps for the first rendition:
- zoom to the extent of the images (the all share the same extent
- turn off all layers except the terrain layer
- open the plugin by –> web –> qgis2threejs –> qgis2threejs
- ensure the terrain layer is the DEM
- keep the rest of the defaults
- hit run
- a browser should open with your data
Try this several time altering the results (i.e. use the surface layers, turn on the ortho photos – resize the output resolution.
We will combine raster data and vector data in this study.